Professor Triggs describes the conditions at Christmas Island as inhumane.

"To state the objective principles of law as a matter of very clear international law: children should not be detained for anything more than what is absolutely necessary for health checks and security checks," she said.

"These children are being detained on what are, on any analysis, prisons at a remote island in shockingly hot, humid and difficult circumstances, in a way that cannot meet what you would imagine would be the standard at an international level."

"The first inquiry was initiated by the court and the court took it on notice that there were human rights concerns about what was happening on Manus. That's the inquiry that has been temporarily adjourned," Mr Webb said.

"The second inquiry relates to information that was specifically presented to the court by the lawyer for 75 asylum seekers on Manus.

"And the court has received that information and used it to commence a second inquiry."

Mr Webb says the National Court is "incredibly powerful", but says it is hard to speculate if it could shut down the Manus Island detention facility if it deems necessary.

"These are the superior courts of a sovereign nation and they're empowered to do all of those things that superior courts are empowered to do," he said.

The Federal Government says it has been informed by the PNG government about the Canning inquiry.

A spokesman for Immigration Minister Scott Morrison says he supports the actions the PNG government considers necessary to take upon their own initiative, within their own sovereign jurisdiction and consistent with their own constitution.

Mr Marles says transparency is the key to ensuring the centre is operating as it should.

"It's obviously important that this is a facility that is run in a way which plays its part in terms of reducing the lives lost at sea," he said.

"But it's also important that it's a facility that does provide safe, secure, humane and dignified accommodation for people who are in it.

"The best way to ensure that is transparency. We have always been concerned about the lack of transparency which has been evident in the way in which the Abbott Government has gone about managing its asylum seeker policy."